Commercial production of poultry (by which is meant chicken and turkey) products destined for sale for consumption customarily is carried out in processing plants. Presently, in about 95% of current processing plants, poultry is brought in by truck in cages from which the poultry is unloaded live by hand or unloaded from the truck by machine and subsequently dumped for further processing. The birds are then hung upside-down on a conveyorized shackle line and their heads are dragged through a brine or water bath. They are then stunned using high voltage electricity just prior to being slaughtered.
Hanging the birds while they are still fully awake can be very troublesome, especially with heavier birds such as tom turkeys which can weigh 40 pounds or more, leading to high labor costs and worker injuries. It is not unusual for the birds to flap their wings, causing joint damage and blood clots in the birds, thus degrading the overall quality of the meat and reducing the yield.
Stunning the poultry with gas as part of the processing regimen presents the advantage that the birds are less likely to engage in extensive movement, thereby reducing the burden to the worker and reducing the risk of damage to the bird. Poultry processors have studied the relative costs of their current methods versus gas stunning and have documented that gas stunning can prevent on the order of $700,000 per shift per year in lost product revenues for a typical turkey processor. Since the majority of processors employ two shifts per day, gas stunning can save on the order of $1.4 million per year.
However, current gas stunning systems are complicated and expensive, with upfront installation costs of 2 to 3 million dollars per line. The installation costs include costs of special cages, mechanized cage handling systems, and additional plant space which usually must be added to the current buildings of the processor.
Thus, there is a need for effective gas stunning techniques, without incurring the complexity and expense of current gas stunning methods and apparatus.